LOS ANGELES, California (CNN) -- University of California students were occupying buildings on several of the system's campuses Friday in protest of a 32 percent tuition hike.

Students had occupied portions of buildings on campuses in Los Angeles, Berkeley, Santa Cruz and Davis late Thursday, and two were still occupied Friday morning.

Student organizers said they would escalate their protests after the system's regents approved the tuition hike during a meeting on the UCLA campus Thursday.

University officials said the $505 million to be raised by the tuition increases is needed to prevent even deeper cuts than those already made because of California's persistent financial crisis.

Protesting students said the hike will hurt working and middle-class students who benefit from state-funded education.

The first tuition hike, which will take effect in January, will raise undergraduate tuition to $8,373. The second hike will kick in next fall, raising tuition to $10,302, said university spokeswoman Leslie Sepuka.

Students who live on campus could pay up to an estimated $17,200, which includes the annual cost of books and housing, according to the system's July 2008 finance guide.

The January increase of about 15 percent is more than double the average public university tuition hike last year. On average, tuition and fees at four-year public universities nationwide increased 6.5 percent, or $7,020, since the previous school year, according to data from College Board.

The university says students whose families make under $70,000 won't be affected by the increases if they are eligible for financial aid.

But students haven't backed down.

On the Santa Cruz campus -- where building occupations began last week with a library sit-in -- about 100 students staged a sit-in in the second-floor lobby of Kerr Hall soon after hearing the tuition hike had been approved, according to UC Santa Cruz Provost David Kliger. Many remained there Friday afternoon.

The demonstrators made demands, Kliger said without listing them.

They would not keep exits clear and broke into some parts of the building, he said, adding they are trespassing and could be arrested. In addition, the students could face suspension or expulsion.

"We cherish the principle of free speech," Kliger said. "Regrettably, these actions go well beyond that."

At UC Berkeley on Friday morning, students occupied the second floor of Wheeler Hall, UC Berkeley spokeswoman Janet Gilmore said. Campus police broke through a barricaded of furniture and office equipment on the ground floor and arrested three students, she said.

She did not know how many students remained in the building, which was closed.

Only a small number of classes were canceled, she said, while others relocated.

Authorities arrested dozens of angry students on the UC Davis campus late Thursday after they refused to vacate the school's administration building.

The 52 students were taken into custody by the Davis Police Department and deputies from the Yolo County Sheriff's Department, according to Claudia Morain, a UC Davis spokeswoman.

The arrests at Mrak Hall came about four hours after the normal 5 p.m. PT (8 p.m. ET) closing time. At one point, as many as 150 students were at the building protesting the tuition increase, Morain said.

UCLA's Campbell Hall was occupied for several hours Thursday evening, a school spokesman said.

The takeover was not planned or sanctioned by the main protest organizer -- the United State Student Association, according to USSA representative Gabby Madriz.

The same building was briefly occupied Wednesday night by several dozen student protesters, according to a UCLA news release. The building was the site of the 1969 shooting deaths of two Black Panther Party members during an internal dispute, according to the release.

The UCLA campus was the scene of the largest and loudest demonstrations Thursday.

"We're fired up. Can't take it no more," students chanted as they marched and waved signs at UCLA. "Education only for the rich," one sign read.

Some faculty members and campus workers -- worried about furloughs and layoffs to come -- joined the protesting students.

"Stop cuts in education and research," a sign carried by a teacher said.

After the regents voted, students rushed to parking decks to stage a sit-in to block regents' vehicles from leaving. Campus police and California Highway Patrol officers in riot gear stood nearby.

As one regent member walked out, students lining his path shouted, "Shame on you, shame on you."

The situation ended without incident as students gradually left the scene.

University executives told the regents the fee hikes are needed because they've already made deep spending cuts in the past two years -- cuts forced by the state budget.

About 26 percent of the $20 billion spent each year by the system comes from the state's general fund coupled with tuition and fees paid by students, according to a summary on the regent's Web site.

The fee increases are to be balanced by a raise in "the level of financial assistance for needy low- and middle-income students," according to a statement from the Board of Regents. The tuition hike is expected to raise $505 million for the university system, and about $175 million of that money is to go toward student financial aid, the board said.

--CNN's Augie Martin and Lynn Lamanivong contributed to this report.

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